A magnetic disk is commonly used in computer systems as a data storage medium. However, before the magnetic disk can be used by a disk drive, the disk must be formatted. The typical magnetic disk may be formatted to contain thousands of "tracks" of information, organized as concentric rings on the disk surface. These tracks must be precisely followed by the disk drive's read/write electronics during the operation of the disk to store information to and read information from the disk's surface. In a typical track following technique, the read/write electronics follow the tracks via servo sectors embedded at regular intervals around the track.
In the case of high track density disks, the tracks are pre-recorded on the disk surface in a factory environment before the disk is suitable for use in a disk drive. Each blank disk is prepared for use by a device commonly referred to as a "servowriter." The servowriter is a machine dedicated to embedding servo signals into the disk's surface. After the servowriter has recorded the servo information in the servo sectors, the disk is checked for quality (e.g., by verifying the accuracy of the servo information). In some instances, for example where the disks are used in removable media drives, the verification process occurs at a separate time and place from the servowriting process at a device sometimes referred to as a verifier.
Often, the servowriter and the verifier need the same data with regard to a particular disk. One particularly important example is the identification of the servowriter used to format a disk. This information is readily available at the time of the disk format. However, after the disk is removed from the servowriter and moved to a different location, the identity of the formatting servowriter may not be readily apparent. This identity becomes significant because, at times, a defective or poorly calibrated servowriter will introduce errors into the formatting process. Unfortunately, in the case of removable media disks, the errors may not be discovered until the disks are checked by the verifier. Tracking the servowriter is difficult because disks are prepared by numerous servowriters. Moreover, those servowriters may be located at a number of different locations. Nevertheless, to ensure maximum disk quality, it is important to be able to trace each disk back to the servowriter that formatted it. In this way, a servowriter that formats poorly can be discovered and corrected. If, for example, a single servowriter is responsible for introducing the majority of bad disks, that servowriter must be identified and corrected.
Some disk manufacturers have used bar codes to trace the disks back to the servowriters and to provide other disk specific information. However, this requires some means for affixing a bar code to the disk, requiring an additional layer of expense and complexity. For example, attaching a bar code will add to the cost of producing each disk, or expensive equipment may be needed to properly track the disks. Moreover, an additional bar code scanning step may be required at the verifier.
An additional example of data needed by both the verifier and the servowriter is media type. A variety of vendors may supply media readable by the same disk drive. Significantly, each of those media may have different characteristics that the verifier, and eventually a user's drive, should recognize. This media type information is also needed by the servowriter during the format process. Applicants have recognized that entering the data once, at the servowriter, and passing the data to the verifier would lead to fewer errors and higher quality.
For the foregoing reasons, applicants have recognized that a method of efficiently passing data between a servowriter and a verifier would translate into substantial cost savings when aggregated over the large volume of disks produced and cut down on errors caused by redundant data entry. Consequently, there is a long-felt need for a method of efficiently transferring disk specific information from a servowriter to a verifier or other devices, such as disk drives.